System and Method for Secured Host-slave Communication

Slave device circuitry for a slave device of a host imaging apparatus, comprising:

• processing circuitry and memory coupled thereto, the processing circuitry configured to:
• determine a new session identification value based upon a stored session identification value in the memory;
• determine a seed value using a secure hash algorithm on a previously determined seed value;
• determine a first number from using the secure hash algorithm on the new session identification value, the determined seed value, and a serial number of the slave device associated with the slave device circuitry;
• identify a slave number from a predetermined portion of a set of bits forming the first number;
• receive a host number from the host imaging apparatus;
• and
• calculate a session key using a hash-based algorithm computation on the host number, the slave number, the new session identification value, and an encryption key maintained in the memory, the session key being a single session key having a first portion for performing encryption and decryption operations on data to be transmitted and data received by the slave device, respectively, and a second portion for generating a new address value of the slave device for communicating with the host.

A method for securely communicating with a host imaging apparatus by a removable supply item thereof, the removable supply item including circuitry and memory, the method comprising:

• determining, by the circuitry, a new session identification value based upon a session identification value stored in the memory;
• updating, by the circuitry, a seed value stored in the memory to obtain an updated seed value;
• determining, by the circuitry, a first number from a result of calculating the new session identification value, the updated seed value, and a serial number of the removable supply item using a secure hash algorithm, the first number comprising a set of bits;
• identifying a slave number from a predetermined number of bits from the set of bits of the first number;
• receiving a host number from the host imaging apparatus;
• and
• calculating a session key using a hash-based algorithm on the host number, the slave number, the new session identification value, and a unique secret encryption key maintained in the memory, the session key being a single session key comprising a first predetermined set of bits and a second predetermined set of bits separate from the first predetermined set of bits, the first predetermined set of bits for performing encryption and decryption operations on data to be transmitted and data received by the removable supply item and the second predetermined set of bits for generating a new address value for the removable supply item to communicate with the host imaging apparatus,
• wherein the circuitry includes or performs as a pseudorandom number generator (PRNG) having an output, the second predetermined set of bits of the session key used for initializing the PRNG, predetermined bits of the output of the PRNG being used to form a portion of the new address value for the removable supply item.